With increasing integration of integrated circuits, electronic devices such as power supply apparatuses are developed toward minimization. As the volume of the electronic device is gradually decreased, the problem associated with heat dissipation becomes more serious. When the power supply apparatus is operated, the electronic components on a printed circuit board may generate energy in the form of heat. If no proper heat-dissipating mechanism is provided to transfer enough heat to the ambient air, the elevated operating temperature may result in damage of the electronic components or reduced operation efficiency. Conventionally, an active heat-dissipation mechanism (e.g. a fan) is used to inhale the external cooling air to cool the electronic components or exhaust the hot air to the ambient air. Alternatively, a large-area heat sink is used to transfer the heat to the surroundings. For example, a metal casing of the electronic device is used as a part of a heat transfer path. The heat generation element is usually fixed on the casing of the electronic device. Since the heat transfer path is the shortest, the heat dissipating efficacy is enhanced.
FIG. 1A schematically illustrates the inner structure of a conventional electronic device. As shown in FIG. 1A, the electronic device 1 includes a metal casing 10, a circuit board 11, at least one heat generation element 12, and a heat dissipating element 13. The metal casing 10 is a box-type casing with an entrance 100, a receiving space 101, and at least one lateral wall 102. For clarification and brevity, only one lateral wall 102 are shown in the drawing. The entrance 100 is in communication with the receiving space 101. The heat generation element 12 is a transistor or any other electronic component that generates heat. Firstly, the heat generation element 12 is mounted on the circuit board 11. That is, the pins (not shown) of the at least one heat generation element 12 are inserted into corresponding conductive holes (not shown) of the circuit board 11. After the circuit board 11 and the heat generation element 12 pass through a reflow furnace (not shown), the heat generation element 12 is securely fixed on the circuit board 11. Then, the circuit board 11 is placed in the receiving space 101 of the metal casing 10 through the entrance 100. In addition, the heat generation element 12 is arranged beside the lateral wall 102. Since there is a gap between the at least one heat generation element 12 and the lateral wall 102, the heat generation element 12 fails to be securely attached on the lateral wall 102. For solving this drawback, a heat dissipating element 13 (e.g. a heat sink or a thermal pad) is interposed between the heat generation element 12 and the lateral wall 102. Afterwards, the heat generation element 12, the heat dissipating element 13 and the lateral wall 102 are combined together through a fixing element 14. For example, the fixing element 14 is a screw. Consequently, the heat generation element 12 can be securely attached on the heat dissipating element 13. Under this circumstance, the heat of the heat generation element 12 is transferred to the heat dissipating element 13 by thermal conduction and then transferred to the large-area lateral wall 102 to be dissipated away.
However, the conventional assembling method still has some drawbacks. For example, while the fixing element 14 is penetrated through the heat generation element 12 and the heat dissipating element 13 and tightened into and the lateral wall 102, a stress may be generated. Due to the stress, the solder paste for welding the pins of the heat generation element 12 is possibly cracked or the pins of heat generation element 12 are possibly damaged. For facilitating tightening the heat generation element 12 into the lateral wall 102 of the metal casing 10, before the circuit board 11 and the heat generation element 12 pass through the reflow furnace, the heat generation element 12 should be fixed by an additional jig (not shown). Consequently, after the circuit board 11 and the heat generation element 12 pass through the reflow furnace, the heat generation element 12 is not shifted. Under this circumstance, the heat generation element 12 can be securely tightened into the lateral wall 102 of the metal casing 10. In other words, the conventional assembling method is more complicated. However, it is found that the position of the heat generation element 12 may still be shifted. Moreover, since the heat generation element 12 has been fixed on the circuit board 11, it is difficult and time-consuming to align the installation positions of the heat generation element 12, the heat dissipating element 13 and the lateral wall 102 with each other. In other words, the conventional assembling method is both complicated and time-consuming.
FIG. 1B schematically illustrates the inner structure of another conventional electronic device. As shown in FIG. 1B, the electronic device 2 includes a metal casing 20, a circuit board 21, at least one heat generation element 22, and a heat dissipating element 23. The metal casing 20 includes an entrance 200, a receiving space 201, and a lateral wall 202. Firstly, the heat generation element 22 is mounted on the circuit board 21. After the circuit board 21 and the heat generation element 22 pass through a reflow furnace (not shown), the heat generation element 22 is securely fixed on the circuit board 21. Then, the circuit board 21 is placed in the receiving space 201 of the metal casing 20. In addition, the heat generation element 22 is arranged beside the lateral wall 202. Then, the heat dissipating element 23 is interposed between the heat generation element 22 and the lateral wall 202. Afterwards, the heat generation element 22, the heat dissipating element 23 and the lateral wall 202 are combined together through a fixing assembly 24.
Please refer to FIG. 1B again. The fixing assembly 24 includes a resilience sheet 240 and a screw 241. The resilience sheet 240 is contacted with a first surface 220 of the heat generation element 22. A second surface 221 of the heat generation element 22 is contacted with the heat dissipating element 23. After the screw 241 is sequentially penetrated through the resilience sheet 240, the heat generation element 22 and the lateral wall 202, the heat generation element 22 is firmly attached on the heat dissipating element 23. Under this circumstance, the heat of the heat generation element 22 is transferred to the heat dissipating element 23 and then transferred to the large-area lateral wall 202 to be dissipated away. In other words, the heat generation element 22, the heat dissipating element 23 and the lateral wall 202 are combined together through the fixing assembly 24 after the circuit board 21 and the heat generation element 22 pass through the reflow furnace. Similarly, it is difficult to interpose the heat dissipating element 23 between the heat generation element 22 and the lateral plate 202. Moreover, the solder paste for welding the pins of the heat generation element 22 is possibly cracked or the pins of heat generation element 22 are possibly damaged.
Therefore, there is a need of providing a heat dissipating module of an electronic device and a method of assembling the heat dissipating module in order to eliminate the above drawbacks.